Lesson (1) Unit (1) Prep (2) Made by: Dr. Niveen Fawzy Oscillatory Motion Lesson (1) Unit (1) Prep (2) Made by: Dr. Niveen Fawzy

Motion & its types Motion: It’s the change in an object’s position as time passes. Types of motion 1- Translational motion 2- Periodic motion First Translational motion Its the motion in which the object’s position is changed relative to a fixed point (or a fixed frame of reference) from time to time between initial & final positions

Examples on translational motion A person’s motion A bicycle’s motion A car’s motion Train’s motion

Second: Periodic motion It’s a motion which is repeated regularly in equal periods of time {moves periodically back & forth over the same path } N.B : It doesn’t have initial & final positions Examples of periodic motion 1-Oscillatory(vibrational) motion 2- Circular motion 3- Wave motion

Concept of Oscillatory Motion Steps: -Push with your hand gently the pendulum & leave it &use stopwatch to record time taken by pendulum to repeat its movement several times Observation: It will move on both sides around its original position (A) The displacement of oscillating body around its original position are equal This motion is repeated in equal time interval -Maximum velocity is at point (A) & decreases gradually when it goes away from point (A), so maximum KE at point (A) Conclusion The oscillatory body moves around its rest point & repeated at equal time intervals

Oscillatory motion  

Note that: Application for oscillatory motion The movement of earth’s crust during earthquakes is considered an oscillatory motion While , The motion of rotary bee is a periodic motion but not considered an oscillatory motion because its not repeated on the 2 sides of its rest point Application for oscillatory motion Microwave oven: Its function depend on the vibration of water molecules in food by effect of microwaves. This oscillatory motion causes the collision of water molecules & this increases its heat Energy in very short time so food is cooked faster

Give reason Food must be put in glass , pottery or ceramic pots while metallic pots are not used Because metallic pots reflect microwaves

Graphical representation of oscillatory motion Tools: -Spring -weight-holder-pencil Steps: 1- Fix pencil to weight , then tie one end to spring 2- let the pencil’s tip touch the mid point of paper tape 3-Roll the paper tape regularly , pull the weight downwards & leave it Observation: The pencil draws the shape of oscillatory motion Conclusion: The simple harmonic motion is the simplest oscillatory motion

The concepts related to oscillatory motion 1- Amplitude 2- Complete oscillation 3- Periodic time 4- Frequency First: Amplitude It’s the maximum displacement done by the oscillating body away from its original position {How far away an oscillating body can get from center} Maximum displacement in a pendulum: AB = BA = BC = CB Each of them is an amplitude Measuring unit (cm) or (m) What is meant by: The amplitude of an oscillating body is 2cm The maximum displacement away from its original position is 2cm

Second: Complete oscillation  

Third: Periodic time  

Fourth: Frequency:  

 

Problems :  

Problem :  

Problems:  

Model answers of book lesson(1) unit(1)  

 

Question (5): X is the motion of string Y is the motion of spring Z is the motion of pendulum